An ethylene-vinyl alcohol copolymer (hereinafter, may be abbreviated as an “EVOH”) is excellent in transparency and gas barrier properties, but has a problem of being poor in stretching properties flexibility, and bending resistance. In order to improve this problem, a method is known in which a flexible resin such as an ethylene-vinyl acetate copolymer or an ethylene-propylene copolymer is blended with the EVOH. However, this method has a problem that the transparency is significantly lowered.
In order to improve the stretching properties, the flexibility, and the bending resistance of the EVOH, Japanese Laid-Open Patent Publication No. 63-230757 has disclosed a resin composition containing two EVOHs (A1) and (B1) The EVOH (A1) has an ethylene content of 20 to 46 mol %, and a degree of saponification of 96 mol % or more The EVOH (B1) has an ethylene content of 24 to 49 mol %, and a degree of saponification of less than 96 mo %. The EVOH (A1) is contained in a ratio of 94 to 30 parts by weight, and the EVOH (B1) is contained in a ratio of 6 to 70 parts by weight. The ethylene content of the EVOH (B1) is larger than the ethylene content of the EVOH (A1) by 4 mol % or more. The degree of saponification of the EVOH (A1) is larger than that of the EVOH (B1) by 3 mol % or more. Furthermore, the ethylene contents and solubility parameters of the EVOH (A1) and the EVOH (B1) satisfy specific formulae. It is described that this resin composition is excellent in rapidly stretchable properties when heated.
WO 02/092643 discloses a modified ethylene-vinyl alcohol copolymer obtained by using a method, in which an ethylene-vinyl alcohol copolymer and a monovalent epoxy compound having a molecular weight of 500 or less are melt-kneaded and reacted with each other in an extruder. This publication describes that the modified ethylene-vinyl alcohol copolymer is superior to an unmodified ethylene-vinyl alcohol copolymer in transparency, stretching properties, flexibility, and bending resistance.
As described above, it is possible to improve the mechanical properties such as stretching properties, flexibility, and bending resistance, and to secure sufficient transparency, by blending EVOHs or modifying an EVOH. However, these methods lower the crystallinity of EVOH, thereby increasing the moisture absorption rate. Thus, after the process of melt molding the obtained resin blend or modified EVOH into a strand, cooling the strand with water, and pelletizing the resultant strand, it is necessary to sufficiently dry the obtained pellets. The obtained resin pellets tend to stick to each other because the pellets absorb moisture. Thus, when these pellets are molten for molding, consideration to an operation or equipment for preventing moisture absorption, or redrying is necessary, and thus the operability is poor.
As a technique for preventing pellets from absorbing moisture, Japanese Laid-Open Patent Publication No. 59-81121 describes a multilayered pellet having a core-shell structure. The multilayered pellet is obtained by using a method in which a molten substance containing an olefin-vinyl alcohol copolymer resin, serving as the core, and a molten substance mainly made of an olefin resin, serving as the shell, are melt-extruded into the shape of a strand and then the strand is cooled and cut. Thus, an olefin-vinyl alcohol copolymer resin that has small melt tension and thus is difficult to extrude into a shape of a strand when employed alone can be pelletized. Thus, the moisture absorption of the pellets can be prevented.
However, when these multilayered pellets are molten for molding, a molded article comprising a resin blend of an olefin-vinyl alcohol copolymer resin and an olefin resin is obtained. This molded article may be poor in transparency. Furthermore, this publication fails to disclose the improvement of stretching properties, flexibility, and bending resistance, which is an object of the present invention.